@deathholes did you ever resolve this issue? I am seeing it with the same Seagate disk on a QNAP NAS :(
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quaylarApr 4 '14 at 19:00

I've changed my Os to saucy, the problem was the uas module. Every time I had to rmmod the uas module before plugging the hard disk. Alternatively you can update the kernel to latest one where the uas is not there
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deathholesApr 5 '14 at 4:31